Elevator control system



Sept. 29, 1931. H. w. WILLIAMS 1,324,856

ELEVATOR CONTROL SYSTEM Filed March 27, 1928 INVENTOR Harald 14/ Williams.

7 AfTORNEY Patented Sept. 29, 1931 UNITED STATES PATENT OFFICE HAROLD W. WILLIAMS, OF EAST PITTSBURGH, PENNSYLVANIA, ASSIGNOB TO WE8TING- HOUSE ELECTRIC Q; IANUFACTURIN G COMPANY, A CORPORATION 01 PENNSYL- VANIA ELEVATOR CONTROL SYSTIIK Application filed larch 27, 1928. Serial Io. 285,003.

My invention relates to motor-control systems and has particular relation to control systems for elevators, hoists and similar machinery. v

An object of m invention is to provide a control system or elevators wherein the control of the direction and speed of the elevator will be actuated in a positive manner.

Another object of my invention is to. provide F. control system for alternating-current elevators wherein direction-and-speed-controlling devices will be positively actuated independently of fluctuations of current in the supply circuit.

Another object of my invention is to provide a control system for alternating-current elevators wherein a single switching device may be used to control the connection of the motor to the supply circuit and also to control the acceleration of the motor.

Another object of my invention is to provide a control system for alternating-current elevators wherein, durin acceleration, the highest possible torque wi 1 be exerted by the motor, but, on deceleration, a dynamic braking effect may be produced by the motor, with a much reduced torque.

Another object of my invention is to provide a control system, as described in the preceding paragraph, wherein the value of the dynamic-braking torque may be adjusted.

My invention may be described with reference to the accompanying drawing, wherein the sole figure is a diagrammatic view illustratingmy s stem of control, as applied to a two-spee alternating-current motor.

In the drawing I have illustrated an elevator car C suitably suspended upon a cable Co which asses over a hoistin drum D to a suitab e counter-weight w. A hoisting motor M is illustrated as being directly coupled to the hoisting drum D, although it is to be understood that suitable gearing may be interposed between the motor and the drum. The motor M is of the squirrel-cage type provided with twospeed windings on the stator, the high-speed winding being designated by the character HS and the low-speed winding by the character LS. The motor M is of the usual twospeed type wherein the respective windings determine the number of poles in the stator of the motor to obtain the several speeds. The ratio of the number of poles to each other may be of any desired value, preferably three to one, that is, the highspeed windin will contain, for exam 1e, 8 poles, while t e low-s eed winding will be used to obtain 24 p0 es.

Suitable direction switches 1 and 2 control the direction in which the motor M will opera-te, by selectivel reversing the phase connections of the higll and low-speed windin s, respectively. The direction switches 1 an 2 are suitably controlled through the actuation of a car switch Ce mounted upon the elevator car C.

The speed windin which will be in operation 1s determine through the actuation of suitable switching devices 3 and 4, illustrated as being of the cam-actuated type operated by pilot motors PL and PH for respectively controllin the connection of the low or the high-speed winding to the source of ower.

suitable source of ower is indicated by conductors I, II an III. The stator windings HS and LS are each star-connected through suitable resistor groups 5 and 6, respectively, which resistors may be shortcircuited by means of additional switching devices actuated by the respective pilot motors PH and PL, respectively.

It is desirable, when starting the elevator car C from rest, with the low-speed winding LS connected for operation, that the greatest possible torque should be exerted by the motor M and, for this reason, I have illustrated sections 7, 8 and 9 of the resistor group 5 as arranged to be shunted from the low-speed-winding circuit during such times as the motor M is acceleratin between zero speed and synchronous spec for the lows eed winding. The resistors 7 8 and 9 are sliunted from the circuit. by means of a relay 10 having its normally closed contact members a, b and 0 connected across the resistors 7, 8 and 9, respectively. The energizing coil for relay 10 is arranged in circuit with a speed governor G, so designed and adjusted as to close its contact members only when the motor M is operating at synchronous speed for the low-speed winding LS. Hence, it is apparent that the resistors 7, 8 and 9 will not be effective to modify the torque exerted by the low-speed winding during such times as the elevator is accelerating with the low-speed winding connected. However, when the motor is operating on the high-speed winding, that is, at a speed above synchronous speed for the low-speed winding, the governor G will maintain its contact membersclosed and, therefore, the shunt around the resistors 7, 8 and 9 will be open. Hence, upon reconnection of the low-speed winding, as by moving the car switch from high-speed operating position to low-speed operating position, (as hereinafter described) the dynamic-braking torque set 11 by the low-speed winding will be gnodihed by the effect of resistors 7, 8 and The advantage of the connection of resistors 7, 8 and 9, just described, will be apparent upon considering the operation of the elevator with a heavy load. It is well known that supplying current to the stator winding of a motor with'a large value of resistance inserted therewith, ,the starting torque exerted by the motor is proportional to the value of voltage supplied to the motor; hence, proportional to the value of resistance in the circuit. Should the torque exerted by the motor be insuflicient to start the load, it is desirable that additional voltage be supplied to the motor to produce the requisite torque. On the other hand, it is desirable, in elevator work, particularly, that some means for setting up a dynamicbraking effect should be provided for use when the motor is decelerating from its high speed to make a stop, and one manner of achieving this result is to reconnect the low-speed winding to the source of power. Since, at this time, the elevator motor is operating at a speed in excess of the synchronous speed of the low-speed winding, a braking torque proportional to the speed of the motor will be exerted. Should the low-speed winding be reconnected and full voltage supplied thereto, this braking torque suddenly applied would be of such high value as to cause a seriousjerk in the operation of the motor and, in elevator application, this jerk or bump is extremely undesirable.

It has heretofore been the practice to reconnect the low-speed winding with such values of resistance in circuit therewith that the initial braking torque exerted by the winding is of very low value and, hence, the braking effect is eased on without creating the objectionable jerk or bump. After reconnecting the winding, however, it is desirable that the braking torque should be increased and, for this reason, it is desirable that the voltage-modifying means, such as resistors, reactors, etc., should be eliminated from the low-speed-winding circuit. However, the maximum braking torque should depend upon the conditions surrounding the motor application, that is, the normal load placed upon the motor, as related to the normal maximum torque for which the motor is designed, and ithas been found desirable to provide some means for adjusting the maximum torque exerted by the motor, when acting as a brake, to the particular loading conditions which exist in the installation.

Prior devices of this character have achieved this result by permanently connecting a section of resistor in circuit with the low-speed winding, thus permanently reducing the maximum torque which may be exerted by this winding, thereby achieving the desired result when the winding is acting to produce a dynamic-brakin effect but having the disadvantage of mo ifying the torque of this winding when the motor is accelerating, at which time it is desirable that all the torque for which the motor is designed should be available for starting and accelerating the load. In my system, therefore, I have provided for both contingencies, namely, rendering the total torque of the motor available for acceleration purposes and for adjustably modifying the torque of the motor during such times as the motor is connected for dynamic braking.

My system will best be understood with reference to an assumed operation of the elevator.

Assuming the elevator car to be in such position in its hatchway as will permit an upward movement thereof, the car switch may be moved in a clockwise direction to complete a circuit for the rip-direction switch 1. This circuit extends from the line conductor II, through conductor 15, contact members 16,17 and 18 on car switch Cs, conductor 19, the coil of up-direction switch 1, conductor 20 and normally closed contact members a on down-direction switch 2 and conductors 21 and 22, to line conductor I. The actuation of up-direction switch 1 supplies current from phase conductors I and II to contact members a and b respectively associated with both switching devices 3 and 4. Neither of the switching devices 3 and 4 has been actuated to close its contact member, however, so motor M does not start at this time.

A further movement of the car switch Cs in the same direction supplies current to the pilot motor PL for actuating switching device 3 to connect the low-speed winding to the source of power. The pilot motor PL is illustrated as of the torque-motor type having its stator windings arranged for connection to the source of ower. Hence, completion of the circuits or the stator windings of the pilot motor PL by movement of the car switch causes this motor to move in a counter-clockwise direction to actuate switch device 3. The circuits for this motor extend from phase conductor I, through conductor 22, contact members 23, 24 and 25, conductor 26, contact members 60 on switching device 4, conductor 26 and one of the phase windings of the pilot motor PL, to the star point 27 for this motor; from phase conductor II, through conductor 15, contact members 16, 17 and 28, conductors 29 and 30, contact members 59 on switching device 4, conductor 30', another of the phase windings of the stator for the motor PL to the star point 27; and from phase conductor III through conductors 31 and 32 to the third phase winding of the motor PL and to the star point 27. Rotation of motor PL engages and operates its associated contact members a and b, by means of cams 33 and 34, respectively. The operation of contact members a and b of switching device 3 will complete circuits supplying current to the low-speed windings LS by way of circuits which extend from line conductor I, through conductors 22 and 35, contact members b on up-direction switch 1 (now closed), conductor 36, contact members a of the switching device 3, conductor 37, one of the phase windings of the low-speed stator Ls, conductor 38, adjustable contact member 39 connecting with resistor section 8, and resistor sections 39' and 40 (constituting part of the group of resistors 5) to starpoint 41; from line conductor II, through conductors 15 and 42, contact members 0 on up-direction switch 1, conductors 43 and 44, contact member 5 on the switching device 3, conductor 45, another of the phase windings of the low-speed stator, conductor 46, resistor sections 9, 47 and 48 of the group 5, to start point 41; and from line conductor III, through conductors 31 and 49, a third phase winding of the low-speed stator, conductor 50, resistor sections 7, 51 and 52, to star point 41.

The motor M will, therefore, startand accellerate on the low-speed-Winding connection. As the pilot motor PL continues to rotate, it engages and actuates its contact members 0 and d by means of cams 53 and 54, respectively. It is assumed that the arrangements of the cams 53 and 54 are such that a predetermined time elapses between the closing of contact members a and b and contact members 0 and 03. Motor PL may be provided with a dash pot T or other suitable retarding device for this purpose. Hence, at a predetermined time after current is supplied to the low-s eed winding LS, resistor sections 40, 48 an 52 will be short-circuited by contact members a and d, thus supplying increased voltage to the windings LS. The motor M will therefore accelerate to the speed determined by the value of volta e so supplied. At a predetermined time t ereafter, contact members e and f will be engaged and 0 rated by cams 55 and 56, respectively, also arranged to engage ano operate the respective contact members at a predetermined time after actuation of the contact members a and d), and resistor sections 39', 47 and 51 will be excluded from the low-speed-winding circuits and the motor will accelerate to substantially its sychronous speed for this winding. It will be observed that, during the time the switches a and d are being actuated, as described, relay 10 is deenergized and, hence, resistor sections 7, 8 and 9 are shunted from the circuit, thus permitting full voltage to be supplied to the windings LS as soon as contact members e and f have been actuated.

Assuming now that the car switch C8 is moved to a further osition in the direction previously described: a circuit will be completed for pilot motor PH to control switching device 4, to supply current to the high- .speed windings. The circuits for the wind-- lngs for the pilot motor PH are in all respects similar to those described for pilot motor PL and will not be completely traced, since it will be readily observed that cur rent from phase conductor I will be supplied to one of the phase windings through contact members 23, 24 and 57 and another phase winding being supplied through contact members 16, 17 and 58. The energizetion of pilot motor PH causes it to rotate in a counter-clockwise direction, closing its contact members a and b for supplying current to the high-speed windings. It will be observed that upon actuation of the contact members a and b, the circuit for the pilot motor PL will be broken at interlocking contact members 59 and 60, and actuated by contact members a and b of switching device 4. Hence, the pilot motor PL will be deenergized and, by gravity or by any other suitable means, will be returned to its inoperative illustrated position.

The circuits for the high-speed windings HS are similar to those described for the low-s ed winding LS, except that each of the p ases of this winding is connected in circuit with resistor sections 61-62, 6364 and 65-66, which terminate in a common star point 67. As the pilot motor continues to operate, contact member cd and e.f will be successively actuated to short circuit resistor sections 626466 and 6163-65 to supply increased voltages to the highspeed winding HS and cause the hoisting motor M to accelerate to substantially synchronous speed for the high-speed winding.

While I have described the operation of the motor M as accelerating first on the lowspeed winding on the high-speed winding, it is to understood that, if desired, the motor may be accelerated from Zero speed to its high speed by direct connection of the highspeed winding without the necessity of first connecting the lowspeed winding. This result is obtained by moving the car switch Cs rapidly to the high-speed-operating position, that is, to a position connecting contact members 23, 24 and 57, etc. r

If it'is now desired to stop the elevator car, car switch Cs will be moved to slowspeed position,-that is to such position as will break contact between contact members 24 and 57, thus deenergizing the windings of pilot motor PH, permitting switching device 4: to return to its oil or illustrated position. In the OE position of switching my device 4, contact members 59 and 60 are reclosed, again energizing pilot motor 'PL, thus reconnecting the low-speed winding LS to the source of power. As previously described, this connection now sets up a dynamic-braking effect. The torque exerted by motor M is modified, however, by the inclusion of all of the resistors in section 5 in the circuit of the winding LS. Asthe motor PL continues to rotate, contact members 0-d and ef will successively short circuit their respective resistor sections,

leaving in circuit only resistor sections 7,

. V8 and 9. Sections 7, 8 and 9, at this time, are not shunted from the circuit since the motor speed, being above that for which the governor G is set, relay 10 is in open-circuit position and, hence, resistor sections 7, 8 and 9 remain in circuit to continuously modify the braking torque during the deceleration period. By adjustably connecting resistor sections 7, 8 and 9, as by adjustable contact members 39, (similar connections being illustrated for the other resistor sections) the modification of torque may be adjusted to fit the particular condition under which the motor M may be operated, that is, it may be adjusted to the normal load on the motor M. In order that the resistor sections 7, 8 and 9 shall not be cut out too soon after motor M reaches free running speed, (substantially synchronous speed) an adjustable dash pot T is provided on relay 10 to retard the closing of the contact member I of the relay, thus obviating the necessity for extremely accurate setting of the gov- 1 ernor switch G.

When the motor speed has been reduced to substantially synchronous speed of the low-speed winding, the car switch Cs may be moved to its illustrated oil position, deenergizing pilot motor PL and up-direction switch 1, at'which time it is assumed that a mechanical brake (not shown) will be applied to bring the motor to rest. While Ihave illustrated the reconnection of lowspec-d winding'LS for dynamic braking as accomplished manually by movement of the car switch Cc to slow-speed position, it is to be understood that any other arrangement may be used, such as providing con-.

tact members on governor switch G to automatically cause reconnection of windings LS independent of the position of car switch The operation of the elevator car C in 7 speed AC elevator equipment and that my invention may be embodiedin' several different forms, such as the combination of switches for connecting the hi lr and lowspeed windings to the source of supply and for operating accelerating resistances in respective circuits; operating switches to connect both the high and low-speed windings in circuit and to control accelerating resistances common to both of the circuits or to operate to control the high and low-speed connections for different directions of operation and for controlling the accelerating resistance in circuit with each of the windings, respectively.

The illustrated and described embodiments of my invention are illustrative only and my system is susceptible to many changesand different modes of application. I, therefore, do not desire to be llmitedto any of the details shown and described, except as defined in the appended claims.

I claim as my invention:

1. In a motor-control system, amultispeed motor having a primary winding for each speed, a source of power, voltage-modifying devices in circuit with said windings,

means for selectively connecting said windings to said source and for excluding said voltage-modifying means from the winding circuits, means operable by movement of said motor at a speed above synchronous speed of the lower-speed winding for preventing exclusion of a portion of the voltage-modifying means for that winding when that winding is connected to said source.

2. In a motor-control system, a multispeed motor having a primary winding for eachrspeed, a source of power, voltagemodifying devices in circuit with said' windings, means for selectively connecting said windings to said source for low-speed operation or a higher-speed operation, a plurality of voltage-modifying means in 011- cuit with one of said lower-speed windings. ,means for including and excluding said voltage-modifying means in said c rcuit, and means operable when said motor is operating at a speed greater than synchronous speed for said winding for preventing exclusion of all of said voltage-modlfymg means.

3. In a motor-control system, a multispeed motor having a primary winding for each speed, a source of power, voltagemodifying devices in circuit with said windings, means for selectively connecting said windings to said source for low-speed operation or a higher-speed operation, a plurality of voltage-modifying means in circuit with one of said lower-speed windings. at least one of which is adjustable, means for including and excluding said voltagemodifying means in said circuit, and means operable when said motor is operating at a speed greater than'synchronous speed for preventing exclusion of said adjustable voltage-modifying means and means for adjusting the value of said voltage-modifying means.

4. In a motor-control system, a multispeed motor having high and low-speed windings, a source of ower, means for selectively controllin t e connection of said windings to said source, accelerating means in circuit with said low-speed windings comprising voltage-modifying means, means for excluding said accelerating means from the winding circuits when said winding is connected to either accelerate or decelerate to the synchronous speed for said winding, and additional voltagemodifying means excluded from said winding circuits when said motor is operating below said synchronous speed and included in said circuit when said motor is operating above said synchronous speed.

5. In a motor-control system, a multispeed motor having high and low-speed windings, a source of power, means for selectively controlling the connection of said windings to said source, accelerating means in circuit with said low-speed windings comprisin voltage-modifying means, means for exclu ing said accelerating means from the winding circuits when said winding is connected to either accelerate or decelerate to the synchronous speed for said winding, and additional voltage-modifying means in circuit with said windings, and speed-responsive means operable to exclude said additional voltage-modifying means when said motor is operating below synchronous speed of the low-speed winding and to include it when said motor is operatingabove said synchronous speed.

6. In a motor-control system, a multispeed motor having high and low-speed windings, a source of power, means for selectively controlling the connection of said windings to said source, accelerating means in circuit with said low-speed windings comprising voltage-modifying means, means for excluding said accelerating means from the winding circuits when said winding is connected to either accelerate or decelerate to the synchronous speed for said winding, and additional voltage-modifyin means in circuit with said winding, an speed-responsive means operable to exclude said additional voltage-modifying means when said motor is operating below synchronous speed of the low-speed winding and to include it when said motor is operating above said synchronous speed, and means for retarding the effect of said speed-responsive means.

7. In a motor-control system, a multispeed motor having high and low-speed windings, a source of power, means for selectively controlling the connection of said windings to said source, accelerating means in circuit with said low-speed windings comprising voltage-modifying means, means for excluding said accelerating means from the winding circuits when said winding is connected to either accelerate or decelerate to the synchronous speed for said winding. additional voltage-modifying means in circuit with said winding, and means operable during the initial stage of the acceleration of said motor for excluding said additional voltage-modifying means from said circuit and operable during the initial stage of the deceleration of said motor for including said additional voltage-modifying means in said circuit.

In testimony whereof, I have hereunto subscribed my name this 20th day of March,

HAROLD W. WILLIAMS. 

